Continuation of Exercise $7\mathrm{.}21.$ Note that in Exercise $7\mathrm{.}21$ there are only four different sample sizes; n $=100,150,200,$ and $250.$ Prepare a control chart that has a set of limits for each possible sample size and show how it could be used as an alternative to the variable$-$width control limit method used in Exercise $7\mathrm{.}21.$ How easy would this method be to use in practice?